scholarly journals Effectiveness of Water Infrastructure for River Flood Management: Part 2 – Flood Risk Assessment and Its Changes in Bangladesh

Author(s):  
Y. Kwak ◽  
M. Gusyev ◽  
B. Arifuzzaman ◽  
I. Khairul ◽  
Y. Iwami ◽  
...  

Abstract. A case study of Bangladesh presents a methodological possibility based on a global approach for assessing river flood risk and its changes considering flood hazard, exposure, basic vulnerability and coping capacity. This study consists of two parts in the issue of flood change: hazard assessment (Part 1) and risk assessment (Part 2). In Part 1, a hazard modeling technology was introduced and applied to the Ganges, Brahmaputra and Meghna (GBM) basin to quantify the change of 50- and 100-year flood hazards in Bangladesh under the present (1979–2003) and future (2075–2099) climates. Part 2 focuses on estimating nationwide flood risk in terms of affected people and rice crop damage due to a 50-year flood hazard identified in Part 1, and quantifying flood risk changes between the presence and absence of existing water infrastructure (i.e., embankments). To assess flood risk in terms of rice crop damage, rice paddy fields were extracted and flood stage-damage curves were created for maximum risk scenarios as a demonstration of risk change in the present and future climates. The preliminary results in Bangladesh show that a tendency of flood risk change strongly depends on the temporal and spatial dynamics of exposure and vulnerability such as distributed population and effectiveness of water infrastructure, which suggests that the proposed methodology is applicable anywhere in the world.

2016 ◽  
Vol 11 (6) ◽  
pp. 1128-1136 ◽  
Author(s):  
Youngjoo Kwak ◽  
◽  
Yoichi Iwami ◽  

Globally, large-scale floods are one of the most serious disasters, considering increased frequency and intensity of heavy rainfall. This is not only a domestic problem but also an international water issue related to transboundary rivers in terms of global river flood risk assessment. The purpose of this study is to propose a rapid flood hazard model as a methodological possibility to be used on a global scale, which uses flood inundation depth and works reasonably despite low data availability. The method is designed to effectively simplify complexities involving hydrological and topographical variables in a flood risk-prone area when applied in an integrated global flood risk assessment framework. The model was used to evaluate flood hazard and exposure through pixel-based comparison in the case of extreme flood events caused by an annual maximum daily river discharge of 1/50 probability of occurrence under the condition of climate change between two periods, Present (daily data from 1980 to 2004) and Future (daily data from 2075 to 2099). As preliminary results, the maximum potential extent of inundation area and the maximum number of affected people show an upward trend in Present and Future.


2021 ◽  
Vol 12 (2) ◽  
pp. 269-291
Author(s):  
Alisa Sahu ◽  
Tushar Bose ◽  
Dipak R. Samal

Urban flooding is growing as a serious development challenge for cities. Urbanization demands the conversion of pervious land to impervious land by pushing the transformation of water bodies, flood plains, wetlands and green spaces into built-up spaces. This affects the hydrological setting of the city’s geographic area. Bhubaneswar, one of the first planned cities of independent India, has expanded rapidly with an increase in the settlement land use cover from 41 km2 to 81 km2 in the last two decades. Non-consideration of disaster risk assessment in the land use plan has placed the city at high disaster risk. Hence, this article explores various avenues for making a flood resilient city through spatial planning. To understand the flood and its consequences, a flood hazard and vulnerability map was prepared by overlaying the existing social and infrastructure networks, and flood risk zones were generated through analytical spatial modelling in GIS. This accounts for the areas in which flood hazards are expected to occur, as well as the area whose socio-economic and infrastructure susceptibility to the disaster is more. The key outcome is to ensure urban development that can work concurrently with nature by integrating disaster risk reduction strategies into land use planning.


Author(s):  
Jose Sergio Palencia Jiménez ◽  
Eric Gielen ◽  
Yaiza Pérez Alonso

The Litoral-Cota 100 zone represents approximately 25% of the total area of the Region of Valencia and concentrates more than 70% of the urban area. One of the consequences of this situation has been the high urban developments produced in the last 50 years. The Comunitat Valenciana has a river flood hazard mapping, according to which, in the Litoral area, more than 80% of the flood hazard is concentrated. As a result of the experienced urban development and the extent of flooding, there is a significant number of people and property exposed to flood hazards. In order to analyze in detail the urban morphology on the coast and its interaction with floods, research has focused on the specific area of the final section of the Girona River, in the province of Alicante. Specifically, in the municipalities of Els Poblets, El Verger, Denia and Beniarbeig, located in the surroundings of the Girona River, very different urban morphologies have been generated that are not adapted to the existing flood hazard. The analysis carried out allows us to conclude that, despite the significant expansion of urban land, existing urban morphology offers ample possibilities to reduce the risk of flooding. It is proposed the integration of overflows in the built city, avoiding the consolidation of non-built land and designing particular measures on affected buildings. These measures of adaptation to the problem will generate a resilient urban morphology.   


Water ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 420
Author(s):  
Zening Wu ◽  
Yuhai Cui ◽  
Yuan Guo

With the progression of climate change, the intensity and frequency of extreme rainfall have increased in many parts of the world, while the continuous acceleration of urbanization has made cities more vulnerable to floods. In order to effectively estimate and assess the risks brought by flood disasters, this paper proposes a regional flood disaster risk assessment model combining emergy theory and the cloud model. The emergy theory can measure many kinds of hazardous factor and convert them into unified solar emergy (sej) for quantification. The cloud model can transform the uncertainty in flood risk assessment into certainty in an appropriate way, making the urban flood risk assessment more accurate and effective. In this study, the flood risk assessment model combines the advantages of the two research methods to establish a natural and social dual flood risk assessment system. Based on this, the risk assessment system of the flood hazard cloud model is established. This model was used in a flood disaster risk assessment, and the risk level was divided into five levels: very low risk, low risk, medium risk, high risk, and very high risk. Flood hazard risk results were obtained by using the entropy weight method and fuzzy transformation method. As an example for the application of this model, this paper focuses on the Anyang region which has a typical continental monsoon climate. The results show that the Anyang region has a serious flood disaster threat. Within this region, Linzhou County and Anyang County have very high levels of risk for flood disaster, while Hua County, Neihuang County, Wenfeng District and Beiguan District have high levels of risk for flood disaster. These areas are the core urban areas and the economic center of local administrative regions, with 70% of the industrial clusters being situated in these regions. Only with the coordinated development of regional flood control planning, economy, and population, and reductions in the uncertainty of existing flood control and drainage facilities can the sustainable, healthy and stable development of the region be maintained.


2013 ◽  
Vol 17 (5) ◽  
pp. 1871-1892 ◽  
Author(s):  
H. C. Winsemius ◽  
L. P. H. Van Beek ◽  
B. Jongman ◽  
P. J. Ward ◽  
A. Bouwman

Abstract. There is an increasing need for strategic global assessments of flood risks in current and future conditions. In this paper, we propose a framework for global flood risk assessment for river floods, which can be applied in current conditions, as well as in future conditions due to climate and socio-economic changes. The framework's goal is to establish flood hazard and impact estimates at a high enough resolution to allow for their combination into a risk estimate, which can be used for strategic global flood risk assessments. The framework estimates hazard at a resolution of ~ 1 km2 using global forcing datasets of the current (or in scenario mode, future) climate, a global hydrological model, a global flood-routing model, and more importantly, an inundation downscaling routine. The second component of the framework combines hazard with flood impact models at the same resolution (e.g. damage, affected GDP, and affected population) to establish indicators for flood risk (e.g. annual expected damage, affected GDP, and affected population). The framework has been applied using the global hydrological model PCR-GLOBWB, which includes an optional global flood routing model DynRout, combined with scenarios from the Integrated Model to Assess the Global Environment (IMAGE). We performed downscaling of the hazard probability distributions to 1 km2 resolution with a new downscaling algorithm, applied on Bangladesh as a first case study application area. We demonstrate the risk assessment approach in Bangladesh based on GDP per capita data, population, and land use maps for 2010 and 2050. Validation of the hazard estimates has been performed using the Dartmouth Flood Observatory database. This was done by comparing a high return period flood with the maximum observed extent, as well as by comparing a time series of a single event with Dartmouth imagery of the event. Validation of modelled damage estimates was performed using observed damage estimates from the EM-DAT database and World Bank sources. We discuss and show sensitivities of the estimated risks with regard to the use of different climate input sets, decisions made in the downscaling algorithm, and different approaches to establish impact models.


2021 ◽  
Vol 6 (2) ◽  
pp. 59-69
Author(s):  
Husna Fauzia ◽  
◽  
Eka Cahyaningsih ◽  
Hery Hariyanto ◽  
Satya Nugraha ◽  
...  

Flooding is a catastrophic phenomenon that can occur due to various factors, such as uncontrolled landuse changes, climate change, and weather anomalies, and drainage infrastructure damage. The Bodri watershed in Kendal Regency is one of the watersheds in Central Java, which is categorized as critical based on Decree No.328/Menhut-II/2009. Some of the problems in the Bodri watershed include land use that is not suitable for its designation, flooding, erosion, and landslides. This study aims to conduct spatial modeling to create flood hazard maps and flood risk level maps in the Bodri watershed. The method used is hydrograph analysis, flood modeling, potential flood hazards, and flood risk levels. Analysis of the potential for flood hazards from the spatial modeling inundation map with the input of the flood peak return period of 2 years (Q2), 5 years (Q5), and 50 years (Q50). Vulnerability analysis based on land use maps of flood hazard areas. The distribution of flood-prone areas in the Bodri watershed is in Pidodo Kulon Village, Pidodo Wetan Village, and Bangunsari Village.


2019 ◽  
Vol 8 (2) ◽  
pp. 55-69 ◽  
Author(s):  
Badri Bhakta Shrestha

Assessment of flood hazard and damage is a prerequisite for flood risk management in the river basins. The mitigation plans for flood risk management are mostly evaluated in quantified terms as it is important in decision making process. Therefore, analysis of flood hazards and quantitative assessment of potential flood damage is very essential for mitigating and managing flood risk. This study focused on assessment of flood hazard and quantitative agricultural damage in the Bagmati River basin including Lal Bakaiya River basin of Nepal under climate change conditions. Flood hazards were simulated using Rainfall Runoff Inundation (RRI) model. MRI-AGCM3.2S precipitation outputs of present and future climate scenarios were used to simulate flood hazards, flood inundation depth, and duration. Flood damage was assessed in the agricultural sector, focusing on flood damage to rice crops. The flood damage assessment was conducted by defining flood damage to rice crops as a function of flood depth, duration, and growth stage of rice plants and using depth-duration-damage function curves for each growth stage of rice plants. The hazard simulation and damage assessment were conducted for 50- and 100-year return period cases. The results show that flood inundation area and agricultural damage area may increase in the future by 41.09 % and 39.05 % in the case of 50-year flood, while 44.98 % and 40.76 % in the case of 100-year flood. The sensitivity to changes in flood extent area and damage with the intensity of return period was also analyzed.


2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Saleh Yousefi ◽  
Hamid Reza Pourghasemi ◽  
Sayed Naeim Emami ◽  
Omid Rahmati ◽  
Shahla Tavangar ◽  
...  

Abstract Catastrophic floods cause deaths, injuries, and property damages in communities around the world. The losses can be worse among those who are more vulnerable to exposure and this can be enhanced by communities’ vulnerabilities. People in undeveloped and developing countries, like Iran, are more vulnerable and may be more exposed to flood hazards. In this study we investigate the vulnerabilities of 1622 schools to flood hazard in Chaharmahal and Bakhtiari Province, Iran. We used four machine learning models to produce flood susceptibility maps. The analytic hierarchy process method was enhanced with distance from schools to create a school-focused flood-risk map. The results indicate that 492 rural schools and 147 urban schools are in very high-risk locations. Furthermore, 54% of rural students and 8% of urban students study schools in locations of very high flood risk. The situation should be examined very closely and mitigating actions are urgently needed.


2021 ◽  
Vol 3 ◽  
Author(s):  
Clémence Poussard ◽  
Benjamin Dewals ◽  
Pierre Archambeau ◽  
Jacques Teller

Studies on inequalities in exposure to flood risk have explored whether population of a lower socio-economic status are more exposed to flood hazard. While evidence exist for coastal flooding, little is known on inequalities for riverine floods. This paper addresses two issues: (1) is the weakest population, in socio-economic terms, more exposed to flood hazard, considering different levels of exposure to hazard? (2) Is the exposure to flood risk homogeneous across the territory, considering different scales of analysis? An analysis of the exposure of inhabitants of Liège province to flood risk was conducted at different scales (province, districts, and municipalities), considering three levels of exposure to flood hazard (level 1- low hazard, level 3- high hazard), and five socio-economic classes (class 1-poorest, class 5-wealthiest households). Our analysis confirms that weaker populations (classes 2 and 3) are usually more exposed to flood hazards than the wealthiest (classes 4 and 5). Still it should be stressed that the most precarious households (class 1) are less exposed than low to medium-range ones (classes 2 and 3). Further on the relation between socio-economic status and exposure to flood hazard varies along the spatial scale considered. At the district level, it appears that classes 4 and 5 are most exposed to flood risk in some peripheral areas. In municipalities located around the center of the city, differences of exposure to risk are not significant.


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